<html>
<body>
  <div>old content</div>
  <div>old content</div>
  <div>old content</div>
  <div>old content</div>
  </body>
  <script type="text/javascript" src="jquery-1.12.0.js"></script>
  <script type="text/javascript">
     $('div').hide();
     $('div').text("new content");
	 $('div').addClass("updatedContent");
	 $('div').show();
  </script>
</html>